Huge Puffback!

franco b wrote:

I'm On Fire wrote:About pouring in vermiculite, I'm not sure how well it'll work.

You can just stuff some fiberglass into the gaps to hold back the mica.

Well, I did stuff some insulation up into the throat.

musikfan6 wrote:This is a very interesting thread, folks. I"ve been reading about these puffbacks now for a while. I guess those of you who have a furnace get a much larger reaction. My FB does something like this, but only if I take the lid off my hopper too fast, or if I open the stove door too quickly. The worst is the lid on the hopper. The first time I did it, the blue flames jumped out of the hole a good 6 inches (the hopper was almost full). I know that might not seem like a lot, but it was enough to scare me. You get that "whoosh" and up come the blue flames. It's quick, but it still takes you by surprise. So of course I've learned my lesson on that. Don't blow yourselves up!

Good day to you all!

I am surprised to read this. I have never had even a hint of puff back from these stoves using all three sizes.

Puff backs occur when gas accumulates faster than it can be exhausted or burned. When you open the door it gets air enough to burn and poof. Because I felt and feel that some over fire air at all times is necessary to burn both initial gas and later carbon monoxide I added air in my stoves by drilling several holes in the lower flange that the stove butts against. They also help in keeping fly ash from accumulating there.

franco b wrote:

musikfan6 wrote:This is a very interesting thread, folks. I"ve been reading about these puffbacks now for a while. I guess those of you who have a furnace get a much larger reaction. My FB does something like this, but only if I take the lid off my hopper too fast, or if I open the stove door too quickly. The worst is the lid on the hopper. The first time I did it, the blue flames jumped out of the hole a good 6 inches (the hopper was almost full). I know that might not seem like a lot, but it was enough to scare me. You get that "whoosh" and up come the blue flames. It's quick, but it still takes you by surprise. So of course I've learned my lesson on that. Don't blow yourselves up!

Good day to you all!

I am surprised to read this. I have never had even a hint of puff back from these stoves using all three sizes.

Puff backs occur when gas accumulates faster than it can be exhausted or burned. When you open the door it gets air enough to burn and poof. Because I felt and feel that some over fire air at all times is necessary to burn both initial gas and later carbon monoxide I added air in my stoves by drilling several holes in the lower flange that the stove butts against. They also help in keeping fly ash from accumulating there.

So then what do you suspect is happening with my stove?? Not enough air?? It doesn't happen every time. It's usually when the hopper is really full.

musikfan6 wrote:So then what do you suspect is happening with my stove?? Not enough air?? It doesn't happen every time. It's usually when the hopper is really full.

The only way I can see that happening is if the hopper was empty when you filled it and then shook down the stove. Normally the coal dispensed from the hopper is partially turned to coke so gas build up is not as severe as in a stove without a hopper. If when you open the top hatch and the hopper is empty, load a smaller amount and then come back in 15 minutes and fill it. The hopper should always have enough coal in it to feed the next shake plus a little more. Top off after every shake.

To add a little air you can do as I did and drill some small holes in the flange that the door butts against. This will mostly aid in burning the gas with a low fire when the thermostat is is set lower. It will also keep the glass cleaner.

The Surdiac which has a similar set up has a series of holes right in the casting that holds the glass.

I've been getting good a predicting puffbacks! Rarely get them, and when I do they are small. I've had some ash blow out of the intake vents before, nothing major. Well, went through the routine of tending the stove today. I was crunched for time so I open the intake a bit more than I normally do. The fresh load of coal was on the larger side. I normally fill in stages with large loads and keep the air dialed down a bit. You could predict the rest of this story! I heard a low woosh from the other room. Walked in to see a light haze of ash floating around the stove. I looked outside and saw a huge ball of ash, HUGE! No need to clean my chimney now . Checked all the flue joints, all is well. Just thought I would brighten everyones day!

Well I'm sad to say I too had a huge puffback or more of a huge explosion The week of warm weather the boiler was idiling along for a couple days. The first day of the each month I turn the oil gun on and run the temps up then switch back to coal mode.I didn't think much of it and shook down then loaded with fresh coal.Well about 2 hrs. later I happened to be sitting directly above the boiler and KABOOM ,and I felt the floor lift under my feet.After wiping myself,I slowly crept down the steps and peeked to see if all was well,the basement was full of sulfur smell and dust,the chimney clean out door blown open,but all was good after checking the pipes.
Next time I run the boiler up with the oil gun,I must remember to put a load on the boiler and make sure the coal bed is glowing before reloading

Hello to all,
I have read 9 pages on puff backs from another thread dating back from 2009, and I just finished these four pages. I still have a question but first I’ll provide a little background.
I installed a Chubby in my fireplace with a manual dampener. It seems to have excellent draft and I’ve been running this stove for over 24 hours now. I have watched the video provided by Chubby Coal Stove Co. twice and everything seems to be going fine with one small exception which I will get to in a bit. First I have to get certain on how to mitigate an explosion as my couch is just over six feet from the stove. I really don’t want to get burned, nor do I want my home to burn down in the event I have one of these episodes.
I think I’m pretty clear on the basics of how this issue occurs, being a buildup of gasses in a compressed area and then an ignition to put it simply. I read several times about the importance of the ‘blue dancing ladies’. I have no issues creating this scenario but by the time I have blue flames after topping off my stove at night the stove temp is rather high, sometimes 600F. If I'm not careful and answered the phone without making the fire first priority, as some could imagine if I forgot about the stove for a bit, it could get much hotter. I just read that I can possibly lower this temp by opening up the secondary air after reloading for a bit, though I have not used the secondary air much at all yet, still experimenting. When I get the stove to idle which is about 400-450, I don’t have blue flames on top of my bed. Although I can see through the little viewing glass that there is a deep orange glow down below the thick new bed of coals I put down. Hours later I still can see the orange glow but not any flames on top.

My question is, once idling is it normal to have my stove operate like so or should I always have some blue flames on top of my coals?

About my one small exception, I read in another thread that someone had an issue with the sliding mechanism for the air intake on their Chubby was slightly bent which resulted in unanticipated operation. Mine does not seem to be bent but I’m only inspecting this with my eyes so I might not be seeing slight gaps.. The left square side is always open more than the right if I do have it open at all. My stove is idling now at 450 F with the air intake fully closed and the manual dampener closed. I know the instructions say to keep that bottom vent open about 1/8 of an inch but to get the stove to idle at these lower temps I found that keeping it closed is allowing it just enough air to run at 450. I put a cigarette right up close to the closed air intake and it seems that the smoke was being sucked in even though the vent was closed. Need I look into this more or am I being excessively concerned with the air intake? I thought that I should be able to put out the fire by cutting off the air but I’m not sure I can do it like this if I wanted to. I suppose I could give it the secondary air which should cool it down if I needed to.

I’m mostly concerned about the chances of a chubby having a blow up, any tips on the chubby stove are very much appreciated.

Thanks,
Gino

GinoF wrote:My question is, once idling is it normal to have my stove operate like so or should I always have some blue flames on top of my coals?

With an idling fire, there usually isn't enough gases or heat to maintain the blue flames even with excessive secondary air. Which is fine, after the initial burning off of hydrocarbons when putting on fresh coal.

GinoF wrote: I thought that I should be able to put out the fire by cutting off the air but I’m not sure I can do it like this if I wanted to.

It doesn't take much combustion air to keep a coal fire alive. Any leaks around the ash pan door or primary air feed could be just enough to keep a fire from going out. If the stove is running too hot with the primary closed, you may want to investigate tightening it up some.

GinoF wrote:I’m mostly concerned about the chances of a chubby having a blow up, any tips on the chubby stove are very much appreciated.

After loading fresh coal (with ash pan door open), I keep my load door propped open a half inch. This keeps the volatile gases diluted so they won't explode.. After the flames show up, I let it burn a little while longer then close the ash pan door. Let the flames subside after closing the ash pan door, then close the load door completely.. Give it a little secondary air to continue providing oxygen to the top of the coal bed to maintain the blue flames with a moderate fire..

Hope this helps ...

GinoF wrote: About my one small exception, I read in another thread that someone had an issue with the sliding mechanism for the air intake on their Chubby was slightly bent which resulted in unanticipated operation.
Gino

I LOVE that phrase "unanticipated operation." I am definitely going to use that one...

Rev. Larry

Thankyou very much Lee for responding, I found your feedback to be very helpful. I hope I never find myself disrespecting coal or rushing out the door without proper startup. From what I've read most instances were from being in a rush. Thanks again and I'll try to stay careful.

GinoF wrote:Thankyou very much Lee for responding, I found your feedback to be very helpful. I hope I never find myself disrespecting coal or rushing out the door without proper startup. From what I've read most instances were from being in a rush. Thanks again and I'll try to stay careful.

Your very welcome partner! One more thing, be sure to never leave the ash pan door open by accident. It's always good advise to never leave the stove unattended while the ash pan door is open unless you have a timer or a thermometer with an alarm. Coal is slow to react but over the course of an hour or less, depending on draft, it can reach dangerous temperatures.

Thanks for all the good advice, I’ve experienced those little puff backs when opening up the loader door to quickly at the wrong time. Just so I’m clear, how long do I want to maintain blue flames before I close the secondary and shut the top damper? I can see this is a routine where not all variables can be held constant. My load of coal came in and it was very much different than the blashack that I was buying by the bag from the local store. This new load varies in size in every bag, I think I’m liking this factor, it seems like the larger pieces allow for some extra air to get through, but the bashack just seems to be denser as though it has more btu’s to it. I understand that both are of the anthracite grade but one is certainly better in terms of burning clean and heat output but seems to have more potential for dangerous puff backs.

Hi Gino, like you stated there are variables
After the fresh coal ignites I let it burn until the entire coal bed has about 8 to 10 inches of blues on top. At that point I let it burn for another 10-15 minutes. Then I'll close the ash pan door and let the blues settle down till they're about 1 to 2 inches high. Then I'm confident about setting air controls for the long burn. I always leave a very small amount of secondary air till the next tending time to help complete combustion of any more hydrocarbons. Secondary air also helps burn Carbon Monoxide later in the burn cycle.

Happy to hear your doing well

This is what my fire looks like after it settles down from initial burn off of hydrocarbons. This is when I set the secondary air control down to a sliver for the long burn.

Hope this helps

Perfect, I'm starting to get the hang of it. Thanks for posting the pics and all the great advice.